Feature: Selectable mongodb engines

[simsekgokhan]

Robomongo to support selecting different versions of mongodb engines.
So, users will be able to select and work with e.g. 2.6 or 3.2 mongodb engines depending on their need.

[corbfon]

Please add 3.4 and 3.6 to the list here 😄it's basically a blocker for me to continue using robo